JP2015102689A - Oscillating element and optical scanning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oscillating element with a highly reliable variable curvature radius mechanism which is less susceptible to failures such as line breakage.SOLUTION: A piezoelectric material 401 has a first surface having a first electrode 501 formed thereon and a second surface having a second electrode 502 formed thereon. A first conductive member 201 is coupled with the first electrode 501, and a first conductive twisting beam 101 is coupled with the first conductive member 201. A second conductive member 202 is coupled with the second electrode 502, and a second conductive twisting beam 102 is coupled with the second conductive member 202. A mirror member 301 is fixed to the piezoelectric material 401 with the first conductive member 201 held therebetween such that a curvature radius thereof changes with deformation of the piezoelectric material 401.

Description

  The present invention relates to a vibration element used for light scanning and the like and an optical scanning device using the vibration element.

  In recent years, MEMS (Micro Electro Mechanical Systems) type vibration elements have been put into practical use and applied to laser beam printers, laser projectors, and the like. The vibration element has a vibrator configured to support the mirror with a torsion bar (torsion beam), and is driven at a drive frequency near the resonance frequency determined by the moment of inertia of the mirror and the spring constant of the torsion beam. The In an optical scanning device using such an oscillating element, an arc sine lens or the like that corrects the focal length according to the scanning angle so that the beam waist of the laser beam is positioned on a predetermined projection surface without depending on the scanning angle This optical system is required.

  Focal length correction can also be realized by a variable focus mirror. According to Patent Document 1, an optical information reading device is proposed in which a variable focus mirror is arranged in an optical system of an optical scanning device and a beam waist scanning position can be changed.

Japanese Patent Laid-Open No. 07-121645

  If a variable focus mirror is arranged instead of an optical system such as an arc sine lens, the optical components related to the correction of the focal length can be simplified. However, if the variable focus mirror is simply arranged, the optical scanning device becomes large.

  In order to reduce the size of the optical scanning device, it is conceivable to integrate the scanning mirror and the variable focus mirror. That is, the mirror itself supported by the torsion beam of the vibration element is used as a variable focus mirror. However, this has the following problems.

  In order to use a mirror supported by a torsion beam as a variable focus mirror, it is necessary to dispose a driving source such as a piezoelectric element on the back surface or the periphery of the mirror member in order to deform the mirror. Furthermore, in order to drive the piezoelectric element, a wiring for supplying power to the drive source from the outside of the vibration element is required. However, in the case of wiring using a wire or the like, there is a problem of disconnection or separation of the joint due to high-speed vibration of the mirror. On the other hand, it is also conceivable to realize wiring by forming a conductive layer on the torsion beam. However, since the maximum stress is applied to the torsion beam at the time of vibration, peeling of the conductive layer can occur particularly in applications where the torsion angle per unit length of the torsion beam is large. When a wide scanning angle is required, it is necessary to lengthen the torsion beam. When it is necessary to reduce the size of the vibration element, it is necessary to narrow the scanning angle. That is, there is a problem that wide-angle scanning and miniaturization cannot be achieved. In addition, in a torsion beam with a wiring layer formed on the surface, the Q value of vibration decreases due to the presence of a layer with a large amount of internal friction on the surface with the largest amount of deformation, or abnormal vibration occurs due to deformation of the torsion beam due to film stress. May occur. A decrease in Q value leads to an increase in power consumption and a decrease in scanning angle. Abnormal vibrations cause fluctuations in the scanning speed of the light, fluctuations in the focal point in the sub-scanning direction, and the like. It cannot be formed accurately at the position.

  Therefore, an object of the present invention is to provide a vibration element that has a highly reliable variable curvature mechanism that is less likely to cause defects such as disconnection.

The present invention is, for example,
A piezoelectric material having a first surface on which a first electrode is formed and a second surface on which a second electrode is formed;
A first conductive member coupled to the first electrode;
A conductive first torsion beam coupled to the first conductive member;
A second conductive member coupled to the second electrode;
A conductive second torsion beam coupled to the second conductive member;
A vibration element comprising: a mirror member fixed to the piezoelectric material so as to sandwich the first conductive member together with the piezoelectric material and having a curvature that changes with deformation of the piezoelectric material. provide.

  According to the present invention, it is possible to realize a vibration element that can vary the curvature with a relatively simple configuration. For example, by forming the two torsion beams themselves from a conductive material, a vibration element having a highly reliable variable curvature mechanism that is unlikely to cause defects such as disconnection is provided.

It is a perspective view which shows an example of a vibration element. It is a block diagram which shows an example of the component of a vibration element. It is the perspective view and block diagram which show an example of a vibration element. It is the perspective view and block diagram which show an example of a vibration element. It is a perspective view which shows the deformation | transformation state of an example of a vibration element. It is the perspective view and block diagram which show an example of a vibration element. It is the perspective view and block diagram which show an example of a vibration element. It is the perspective view and block diagram which show an example of a vibration element. It is a top view explaining operation | movement of an optical scanning device. It is a graph which shows the drive signal of an optical scanning device. It is a top view explaining operation | movement of an optical scanning device. It is a graph explaining operation | movement of an optical scanning device. It is a graph explaining operation | movement of an optical scanning device. 1 is a diagram illustrating an example of an image forming apparatus. It is a figure which shows an example of an image projector. It is a figure which shows an example of an optical pattern reader.

[Optical scanning device]
FIG. 1A illustrates an optical scanning device 1. FIG. 1B illustrates the configuration of the vibration element 11. The vibration element 11 includes a vibration portion 21 and a first torsion beam 101 and a second torsion beam 102 having conductivity to support the vibration portion 21 so as to be capable of swinging (rotating vibration). The vibration unit 21 includes a conductive member, a piezoelectric material, a mirror member, and a magnet. The vibrating portion 21 in this example includes a flat plate-like first conductive member 201, a ring-shaped second conductive member 202, a piezoelectric material 401 sandwiched between them, and a mirror attached to the first conductive member 201. It has a member 301, a first magnet 601 and a second magnet 602 attached to the second conductive member 202. Thus, since the mirror member 301 is provided on at least one electrode side of the piezoelectric material 401, the curvature of the mirror surface changes due to the deformation of the piezoelectric material 401.

  Further, each end portion (base end portion) of the first torsion beam 101 and the second torsion beam 102 is fixed to a housing (not shown). The other end portions (tip portions) of the first torsion beam 101 and the second torsion beam 102 are respectively coupled to, joined to, connected to, or fixed to the first conductive member 201 and the second conductive member 202. ing. The reflection direction of the mirror member 301 of the vibration part 21 is changed by the torsional deformation of the first torsion beam 101 and the second torsion beam 102, and optical scanning is performed.

  A magnetic field generation unit 700 is disposed in the vicinity of the vibration unit 21, and rotational torque is generated in the first magnet 601 and the second magnet 602 by the alternating magnetic field generated based on the drive signal from the drive circuit 801, Rotational vibration is excited in the vibration part 21. The first torsion beam 101 and the second torsion beam 102 are electrically connected to the first conductive member 201 and the second conductive member 202, respectively, without wiring or the like.

  In addition, a first electrode 501 is formed on the first surface of the piezoelectric material 401, and the first conductive member 201 is coupled to the first electrode 501. A second electrode 502 is formed on the second surface of the piezoelectric material 401, and the second conductive member 202 is coupled to the second electrode 502. Thus, the piezoelectric material 401 functions as a piezoelectric body having a piezoelectric layer interposed between a pair of electrodes. With respect to the rotation axis of the vibration element 11, the first conductive property is aligned with the center line extending in the longitudinal direction of the first torsion beam 101 and the center line extending in the longitudinal direction of the second torsion beam 102. The connecting portion of the first torsion beam 101 to the member 201 and the connecting portion of the second torsion beam 102 to the second conductive member 202 are respectively bent. The first torsion beam 101 and the second torsion beam 102 are each connected to a drive circuit 802 that supplies electric power. Thus, the first torsion beam 101 and the second torsion beam 102 function as a pair of conductive beam portions.

  Then, the first torsion beam 101 and the second torsion beam 102 send the drive signals supplied from the drive circuit 802 to the piezoelectric material 401 via the first conductive member 201 and the second conductive member 202, respectively. Application is made to the first electrode 501 and the second electrode 502. As a result, an electric field is generated between the first electrode 501 and the second electrode 502 of the piezoelectric material 401, and the piezoelectric material 401 expands and contracts according to the electric field to cause deformation of the first conductive member 201 and the mirror member 301. Let

  Thus, the vibration part 21 having the piezoelectric material 401 and the mirror member 301 functions as a variable curvature mirror. The curvature of the mirror member 301 is controlled by the magnitude of the drive signal from the drive circuit 802, and the focal position of the scanning light is corrected. As a result, the position of the beam waist matches the irradiation target position.

[Vibration element]
In the vibration element 11 shown in FIGS. 1A and 1A, the first torsion beam 101 and the second torsion beam 102 exist on different sides of the piezoelectric material 401 and the mirror member 301, respectively. The mirror member 301 is supported at both ends. However, such a configuration is only an example. Another embodiment of the vibration element 11 will be described with reference to FIGS.

  FIGS. 2A and 2B illustrate the vibration element 12 having a configuration in which the first torsion beam 101 and the second torsion beam 102 are arranged in parallel (so-called cantilever support). The ends of the first torsion beam 101 and the second torsion beam 102 are both fixed to the casing, and the central axis (rotation axis) of the rotational vibration of the vibration element 12 is the first torsion beam 101 and the second torsion beam. It is in the middle of the beam 102.

  In the cantilever support structure as shown in FIG. 2, if the bending rigidity of the torsion beam is too low, the resonance frequency of the bending mode in which the mirror member 301 swings in the y direction of the coordinate axis shown in FIG. For this reason, the vibration state of the vibration unit 21 becomes a vibration state in which a bending vibration mode is added to the rotation vibration mode due to an external impact or the like, and the scanning line may fluctuate in the sub-scanning direction (z direction).

  As shown in FIG. 2, in the configuration in which the first torsion beam 101 and the second torsion beam 102 are arranged in the y direction, the flexural rigidity increases, and therefore the resonance frequency of the flexural vibration increases. That is, even if an impact is applied from the outside, it is difficult to change, and even if it changes, the change can be attenuated in a short time.

  In FIGS. 3A and 3B, twist beams are arranged on both sides of the first conductive member 201 and the second conductive member 202. That is, in the vibration element 13, a third torsion beam 103 and a fourth torsion beam 104 are further added to the vibration element 12. The first torsion beam 101 and the third torsion beam 103 are coupled to the first conductive member 201 from opposite sides. Similarly, the second torsion beam 102 and the fourth torsion beam 104 are coupled to the second conductive member 202 from opposite sides. The longitudinal center line of the first torsion beam 101 and the longitudinal center line of the third torsion beam 103 coincide with each other. Similarly, the longitudinal center line of the second torsion beam 102 and the longitudinal center line of the fourth torsion beam 104 coincide with each other. In FIG. 2 and FIG. 3, there is a space between the first torsion beam 101 and the second torsion beam 102 because no bending is performed. Of course, bending may also be adopted for the first torsion beam 101, the second torsion beam 102, the third torsion beam 103, and the fourth torsion beam 104.

  The structure of the vibration element 13 shown in FIG. 3 is a kind of a double-support structure, and the overall size is larger than that of the structure of FIG. 2, but the flexural rigidity is higher and the scanning line in the sub-scanning direction is increased. Variation can be suppressed.

  FIG. 4 shows an example of the shape when the vibration member 13 deforms the mirror member 301 by applying a voltage to the piezoelectric material 401 through the torsion beam. Due to the curvature of the piezoelectric material 401 and the mirror member 301, the conductive members 201 and 202 are also deformed, and the influence also affects the torsion beams 101 to 104. There is no problem when a large amount of deformation is not required as the curvature change, that is, when the rotation axis of the vibration part 21 is within the cross section of the torsion beams 101 to 104. However, when a large change in curvature is required, abnormal vibration in which bending vibration is added to the normal rotational vibration mode may occur due to deformation of the torsion beams 101 to 104.

  On the other hand, as shown in FIG. 5, the first conductive member 201 and the second conductive member 202 are electrically conductive so as to be held at two symmetrical positions apart from the rotational axis of the rotational vibration. The holding portions 701, 702, 703, and 704 may be formed. Note that the first holding portion 701 is coupled to the first torsion beam 101 and is coupled to the first conductive member 201 at two points. The second holding portion 702 is coupled to the first torsion beam 102 and is coupled to the second conductive member 202 at two points. The third holding portion 703 is coupled to the third torsion beam 103 and is coupled to the first conductive member 201 at two points. The fourth holding portion 704 is coupled to the fourth torsion beam 104 and is coupled to the second conductive member 202 at two points.

  Magnets 603 and 604 having the same thickness as the piezoelectric material 401 are provided as spacers. That is, the magnet 604 is sandwiched between the first holding unit 701 and the second holding unit 702. Similarly, the magnet 603 is sandwiched between the third holding portion 703 and the fourth holding portion 704. Magnets 603 and 604 are provided instead of magnets 601 and 602. By providing the holding portion in this manner, the holding portion functions as a buffer material for changing the curvature. Therefore, the curvature change of the mirror member 301 or the like hardly reaches the torsion beam, and the occurrence of abnormal vibration can be reduced.

  6A and 6B show a vibration element 15 obtained by developing the vibration element 14. Both the first conductive member 203 and the second conductive member 204 of the vibration element 15 have a frame shape. Note that the outer shapes of the first conductive member 203 and the second conductive member 204 substantially match the outer shape of the piezoelectric material 401. In this example, the first conductive member 203 is composed of a plurality of frames. The first frame 711 is a frame that extends in the lateral direction and is coupled to the first torsion beam 101 (second torsion beam 102). Each of the second frame 712 and the third frame 713 extends in the vertical direction, and is a frame coupled to the first frame 711 and the fourth frame 714. The fourth frame 714 is a frame extending in the lateral direction and coupled to the third torsion beam 103 (fourth torsion beam 104). Since the first conductive member 203 and the second conductive member 204 have the same shape, mass production is easy. The mirror member 301 is formed with grooves 723 and 724 that receive part of the second frame 712 and the third frame 713 of the first conductive member 203. The magnet 603 is sandwiched between the fourth frame 714 of the first conductive member 203 and the fourth frame 714 of the second conductive member 204. The magnet 604 is sandwiched between the first frame 711 of the first conductive member 203 and the first frame 711 of the second conductive member 204.

  A metal material can be used as the material of the conductive member. However, if the volume of the conductive member becomes too large, the weight of the vibration part increases. As a result, the resonance frequency of the flexural vibration mode may decrease, causing the scanning line to fluctuate in the sub-scanning direction or cause abnormal vibration. In addition, since the moment of inertia of the vibration part also increases, the stress load on the torsion beam increases, which may cause a problem in durability. On the other hand, a frame-like conductive member is employed as the first conductive member 203 and the second conductive member 204 like the vibration element 15 shown in FIGS. 6A and 6B. Thereby, the vibration part 21 can be reduced in weight. In the vibration element 15, it is preferable that the Young's modulus of the second frame 712 and the Young's modulus of the third frame 713 accommodated in the mirror member 301 and the grooves 723 and 724 formed thereon are matched. The amount of change in the curvature of the mirror member 301 due to expansion and contraction of the piezoelectric material 401 varies depending on the Young's modulus and thickness of the member coupled to the piezoelectric material 401. Therefore, if there is a large difference between the Young's modulus of the second frame 712 and the Young's modulus of the third frame 713 of the first conductive member 203 fixed in the mirror member 301 and the grooves 723 and 724, the curvature varies depending on the position. Occurs. If the Young's modulus of the second frame 712 and the Young's modulus of the third frame 713 are close to the Young's modulus of the mirror member, the influence on the curvature is further reduced. Therefore, a material that is close to the Young's modulus of the mirror member 301 may be selected as the material of the second frame 712 and the third frame 713. Alternatively, when a metal material is used as the material of the first conductive member 203, the Young's modulus of the first conductive member 203 may be brought close to the Young's modulus of the mirror member 301 by a processing rate or heat treatment.

  The configuration in which a part of the first conductive member 203 is accommodated in the grooves 723 and 724 formed in the mirror member 301 shown in FIG. 6 may be further improved. According to FIG. 7, the vibration element 16 is configured by intersecting the second frame 712 and the third frame 713 of the vibration element 15. Note that the grooves 723 and 724 of the mirror member 301 also intersect with each other in order to accommodate the intersecting second frame 712 and third frame 713. Thereby, the difference between the curvature distribution in the scanning direction and the curvature distribution in the sub-scanning direction can be reduced.

  In the vibration element 15 shown in FIG. 6, the influence of the grooves 723 and 724 can greatly affect the curvature distribution in the scanning direction. On the other hand, in the vibration element 16 shown in FIG. 7, the curvature distribution in the scanning direction and the curvature distribution in the sub-scanning direction are substantially the same. Therefore, the vibration element 16 can perform optical scanning more stably than the vibration element 15.

[Materials]
The material used for the torsion beam is not particularly limited as long as it is a conductive material such as a resin material mixed with carbon in addition to a metal material, but from the viewpoint of repeated durability and impact resistance, SUS301 and SUS631. Metal materials such as stainless steel, copper alloy, and Co (cobalt) -Ni (nickel) base alloy may be employed. Among these, age-hardening type Co-Ni based alloys such as Co-Ni-Cr (chromium) -Mo (molybdenum) alloys represented by SPRON (registered trademark) 510 have a particularly high fatigue limit and are subjected to repeated stress. Is convenient. In addition, since the Co—Ni-based alloy has high heat resistance and corrosion resistance, it is unlikely that energization or heat generated by it will affect the material characteristics, which is also appropriate for an optical scanning apparatus that energizes a torsion beam. Let's go. Furthermore, the Co—Ni base alloy has a feature that the internal friction is small, and has a high Q value when the vibration elements 11 to 16 are caused to resonate and rotationally vibrate, and there is an advantage that power consumption required for driving can be reduced. In the case of using a Co—Ni—Cr—Mo alloy, after a work hardening treatment is performed by rolling or drawing at a working rate of 50% or more, more preferably 90% or more, shape processing is performed, Age hardening treatment may be performed at a temperature of about 600 ° C. The final Young's modulus and hardness can be adjusted by the processing rate and the aging heat treatment temperature and time. For the shape processing, etching processing, press processing, laser processing, wire electric discharge processing or the like can be used. In work hardening processing and shape processing, depending on the finish, internal friction near the surface may increase and the Q value of the vibration element may decrease. In such a case, it is better to perform an etching process before age-hardening treatment, and after performing shape processing larger than the target dimension, finish shape processing is performed using a nitric acid-based etchant or the like. preferable. In addition, even when there are minute cracks or surface roughness that occur during work hardening or shape processing, problems such as a decrease in Q value and durability of the vibration element occur. In such a case, electropolishing is preferably performed before age hardening, and the surface is preferably smoothed by electropolishing using a phosphoric acid-based or ethylene glycol-based liquid.

  The conductive members 201 to 204 are preferably made of the same material as the torsion beam and have an integral structure from the viewpoint of productivity. However, the present invention is not limited to this, and it may be formed of a conductive material such as a metal material and joined to the torsion beam. When joining, it is preferable to use a wire rod for the torsion beam because the shape processing can be simplified, and for the purpose of improving the durability of the joint portion, a joining surface is formed by forging etc. Is preferred.

  For the piezoelectric material (piezoelectric layer) 401, lead zirconate titanate (PZT) having a large piezoelectric constant is suitably used. However, the material is not limited to this, and any material having piezoelectric characteristics such as barium titanate, lead titanate, lead niobate, or the like may be used. As long as the piezoelectric material 401 can be formed into a film in addition to a sintered body having electrodes formed on both surfaces, the conductive members 201 to 204, the mirror member 301, the mirror member 301 containing the conductive member 203, or the like. It may be formed by film formation on a composite configuration of a conductive member and a mirror member. In the case of using a sintered body, the piezoelectric material 401 is held by direct bonding of the electrodes 501 and 502 and the conductive members 201 to 204 or by bonding using an adhesive or the like. In the case of bonding, the facing area is increased as much as possible and the bonding layer is thinned so that the electric capacity between the conductive member and the electrode in the bonding portion is larger than the electric capacity between both electrodes of the piezoelectric material 401. Thus, it is preferable to bring the conductive member and the electrode close to each other. Moreover, conductivity may be imparted to the adhesive to ensure conductivity. In the case of forming by film formation, the film is formed directly on the conductive members 201 to 204, and no electrode is formed therebetween. As a film formation method, various film formation methods such as a sol-gel method can be used. Among them, an aerosol deposition method and a gas deposition method are used which are easy to form a thick film with a high film formation rate and good film quality. Is preferred. When PZT is used as the material of the piezoelectric material 401 and a metal material is used for the conductive members 201 to 204, an intermediate layer for preventing lead diffusion may be formed. In order to improve the piezoelectric characteristics, it is effective to raise the heat treatment temperature. Therefore, it is preferable that the conductive members 201 to 204 serving as a film formation base material be formed of a material having high heat resistance, and a Co—Ni base. An alloy or the like is preferably used. It should be noted that the mirror member 301 is made to be a variable curvature movable mirror (such as a deflection mirror) by driving deformation of a piezoelectric body (piezoelectric element) obtained by interposing a piezoelectric material 401 between the electrode 501 and the electrode 502 as a pair of electrodes. It becomes possible to do.

  The mirror member 301 may be a reflection film directly formed on the conductive member 201 in addition to a reflection film or an increase reflection film formed on a base material with good surface flatness such as a silicon wafer or thin glass. Examples of the reflective film include films of Au, Ag, Al, etc. formed by vapor deposition. Further, a reflective reflection film is formed thereon as necessary. Further, a mirror surface can be formed by polishing the conductive member 201. In this case, the conductive member 201 also functions as the mirror member 301.

  The magnets 601 to 604 are not particularly limited, but are preferably as small and strong as possible in order to reduce the moment of inertia related to torsional vibration. Therefore, an Nd—Fe—B magnet or Sm—Co magnet having a strong magnetic force, an Fe—Cr—Co magnet excellent in workability capable of forming a small shape, or the like can be suitably used.

[Operation of optical scanning device]
Next, the operation of the optical scanning device will be described with reference to FIGS.

  FIG. 8A shows a state of laser beam scanning by an optical scanning device employing any of the vibrating elements 11 to 16. FIG. 8B shows a state of deformation of the mirror member 301 disposed in the vibration part 21, and is a common deformation in the light scanning direction and the sub-scanning direction perpendicular thereto. When the mirror member 301 has a curvature such as (R1) in FIG. 8B due to the electrical signal applied to the piezoelectric material 401, the beam waist of the projection surface P1 whose distance is R1 from the scanning center is shown. Assume that it is located in the center. When the vibrating portion 21 is rotated by the torsional vibration of the torsion beam to reach the state of (R1 ′) in FIG. The beam waist is positioned at the right end of the projection plane P1 at a distance R1 ′ from the scanning center. If the curvature does not change from the state (R1), the beam waist is at the position R1 in the scanning end direction, and the beam diameter expands at the right end of the projection plane P1. Similarly, the beam waist is held on the projection plane P1 by changing the curvature in the state of (R ″) in FIG. 8B at the left end of the scan. Without using a lens optical system such as an arc sine lens, by controlling the mirror curvature using a signal including a frequency twice as high as the scanning frequency Optical scanning is possible in which the beam waist position where the minimum spot is formed is held on substantially the same plane, as shown in FIG. FIG. 8 shows a deformed state of the mirror member 301 for maintaining the state where the curvature is larger than that in FIG. 8B, so that the beam waist position is (R2) → (R2 ′) → (R2) → ( R2 ") → (R ) When you move. As described above, the surface holding the beam waist can be changed by controlling the drive signal of the piezoelectric material 401.

  FIG. 9 is an example of a drive signal for performing scanning as shown in FIG. When the drive circuit 801 supplies a drive signal having the frequency f1, rotational vibration is induced in the vibration unit 21. On the other hand, the drive signal generated by the drive circuit 802 adding the offset voltage ΔV to the signal having the frequency f2 twice the frequency f1 is applied to the torsion beam. Thereby, the curvature deformation of the mirror member 301 is induced.

  The drive signal of frequency f2 is a drive signal for maintaining the beam waist on the scan plane within one scan, and ΔV is an offset for changing the plane holding the beam waist. When the vibration unit 21 is rotationally vibrated by resonance, the phase of the drive signal having the frequency f1 and the rotation angle of the vibration unit 21 are shifted by 90 degrees. Therefore, the phase of the drive signal output from the drive circuit 802 is also shifted from the phase of the drive signal output from the drive circuit 801 so that the curvature deformation of the mirror member 301 of the vibration unit 21 is controlled in accordance with the rotation angle.

  Next, the moving speed of the beam spot formed on the projection surface will be described. The optical scanning device changes the beam intensity based on the time series data while scanning the beam, or detects the change in the intensity of the reflected light during the beam scanning as the time series data. Read the optical pattern. At this time, if the moving speed of the beam changes greatly, image distortion and variation in reading resolution occur. A method of correcting the time-series data so that the change in the beam intensity corresponds to the change in the moving speed of the beam or a method in which the reading speed corresponds to the change in the moving speed can be considered, but this requires expensive high-speed control means. It becomes. The movement of the beam spot on the projection surface is preferably as constant as possible, and within a range in which constant velocity on the projection surface can be obtained with respect to the beam scanning angle of the vibrating elements 11 to 16 that change in angle in a sine wave shape. It is preferred to use.

  FIG. 10 shows the state of optical scanning as in FIG. Projection plane located at a distance L from the scanning center, with θo being the maximum scanning angle of the beam due to rotational vibration of the mirror member 301 with reference to the center of scanning, and θeff being the effective range in which scanning light is actually used. A range corresponding to θeff on P is Xeff. Assuming that the projection plane P is P1 in FIG. 8A, the position of Xeff corresponds to the position of R1 'at the end of the projection plane P1. When the beam direction is the direction of the angle θ and the moving speed of the beam spot formed on the projection plane P is V, the moving speed V with respect to the angle θ is based on the moving speed Vo when the angle θ = 0. The rate of change V / Vo is as shown in FIG. In FIG. 11A, the horizontal axis represents the angle θ indicating the direction of the beam, and the vertical axis represents the rate of change V / Vo of the moving speed V. As the maximum scanning angle θo is increased, the moving speed V with respect to the angle θ changes as shown in (i) to (v) of the figure. At this time, if the allowable error of the spot moving speed is Δv, the angle within this range in the graph of (iii), that is, the effective scanning angle θeff is Θ3. In the graph (iv) in which the maximum scanning angle is increased, the effective scanning angle is expanded to Θ4. However, in the graph (v) in which the maximum scanning angle is further increased, the effective scanning angle becomes Θ5 and narrows conversely. Even if the maximum scanning angle is increased further, the effective scanning angle cannot be expanded. FIG. 11B shows the relationship between the maximum scanning angle θo and the effective scanning angle θeff, and the maximum scanning angle at which the effective scanning angle becomes the widest differs depending on the size of the allowable error. FIG. 11C shows the maximum effective scanning angle with respect to the size of the allowable error and the maximum scanning angle necessary for obtaining the effective scanning angle. Although there is a difference due to an allowable error, a maximum scanning angle of 40 degrees or more is required to obtain the maximum effective scanning angle. In an optical scanning device, it is desirable that a wide range of image formation and reading can be performed with a short projection distance, and the effective scanning angle is preferably as wide as possible. Moreover, it is preferable that the maximum scanning angle is as narrow as possible from the viewpoint of miniaturization of the vibration elements 11 to 16 and power consumption. For these reasons, it is preferable to operate the vibration element at the maximum scanning angle at which the effective scanning angle reaches a peak. For this purpose, the maximum vibration angle is ± 40 degrees or more with respect to the center of the scanning, and the rotational vibration amplitude of the vibration element. Is preferably ± 20 degrees or more. In order to achieve this amplitude with a small vibration element, the torsion beam supporting the mirror member 301 needs to have high strength and durability, and the torsion beam using the age-hardening type Co—Ni based alloy is from this point. Is also highly preferred.

  Next, changes in the beam spot diameter projected onto the projection surface during optical scanning will be described. In an optical scanning device, the beam spot diameter greatly affects the definition of an image formed or projected by optical scanning and the resolution of optical pattern reading. For this reason, it is preferable that the variation of the beam spot diameter within the effective scanning region is as small as possible.

  FIG. 12A shows an example of a change in the beam spot diameter depending on the position on the projection surface. 10 shows a change in beam spot diameter when the projection distance L shown in FIG. 10 is set to 174 mm and the beam spot is moved in the x-axis direction from the center O of the projection surface by the rotational vibration of the vibrating elements 11 to 16. The horizontal axis of FIG. 12A is the distance x from the center of the projection surface, and the vertical axis is the beam spot diameter φ. FIG. 12B shows an example of a drive signal applied to the piezoelectric material 401 in order to change the curvature of the mirror member 301. The drive signal having the frequency f2 is a drive signal having a frequency f2 that is twice the frequency of the rotation vibration of the vibration elements 11 to 16, that is, the scanning frequency (rotation vibration frequency) f1, and the drive signal having the frequency f2 shown in FIG. Is the same. The drive signal of frequency f4 is a signal having a frequency f4 that is four times the frequency f1, and the drive signal of frequency f2 + f4 is a signal obtained by superimposing the drive signal of frequency f2 and the drive signal of frequency f4 at an appropriate ratio. The change of the beam spot diameter depending on the position on the scanning plane is shown in the graph of “no f2” in FIG. 12A when the mirror deformation synchronized with the scanning frequency is not performed. The spot diameter increases rapidly. On the other hand, when the curvature of the mirror member 301 is changed by the drive signal of the frequency f2, it is as shown in the graph of “only f2” in FIG. 12A, and within the effective scanning range of Xeff. The fluctuation of the beam spot diameter can be greatly suppressed. Further, when the curvature of the mirror member 301 is changed by a drive signal in which the frequencies f2 and f4 are superimposed, the graph is shown in the graph “f2 + f4” in FIG. 12A, and is almost independent of the position. A constant beam spot diameter can be obtained.

  The above-described effects of constant velocity and beam spot diameter stabilization can be obtained only when the vibrating elements 11 to 16 can perform stable optical scanning without causing abnormal vibration or the like. By appropriately setting the maximum scanning angle using the vibration elements 11 to 16 and controlling the curvature of the vibration part 21 with a signal having a frequency twice and four times the scanning frequency, image formation and projection, An optical scanning device capable of reading an optical pattern with high accuracy can be realized.

[Image forming apparatus]
FIG. 13 shows an image forming apparatus 7 which is an embodiment of an optical scanning device. The vibration element 10 is any one of the vibration elements 11 to 16 described above, and the configuration around the vibration unit is omitted. The light source 971 emits light whose intensity is modulated based on the drive signal output from the control circuit 970 according to the image data. The emitted light is reflected by the mirror member 301 of the vibration element 10 through the emission optical system 972, and scans on the photoconductor 975 which is an example of an image carrier. The scanned light is detected by BD sensors 973 and 974. The control circuit 970 generates and outputs a control signal for controlling the scanning angle based on detection signals output from the BD sensors 973 and 974. The control signal is fed back to the drive circuit 801 of the drive circuit 870 of the vibration element 10. As a result, the drive circuit 801 stably maintains the maximum scanning angle of the vibration element 10 at an appropriate value. A drive circuit 802 included in the drive circuit 870 outputs a control signal for controlling the mirror curvature based on the detection signal. Thereby, the beam spot diameter on the photosensitive member 975 is maintained at a substantially constant size.

  The image forming apparatus 7 using the vibration elements 11 to 16 is less likely to cause disconnection or abnormal vibration, and can perform stable optical scanning and mirror curvature control. For this reason, the effects of constant speed and stabilization of the beam spot diameter are exhibited by optimizing the maximum scanning angle and optimizing the mirror curvature control signal. That is, highly accurate and reliable image formation is possible. Further, in the image forming apparatus 7 using the vibration elements 11 to 16, the lens optical system for correcting the variation in the scanning speed can be simplified. In addition, it is not necessary to correct the image data or the intensity modulation signal of the laser beam in order to cope with fluctuations in the scanning speed. Thereby, a small and inexpensive image forming apparatus can be realized.

[Image forming apparatus]
FIG. 14A shows an image projection apparatus 8 which is an embodiment of the optical scanning apparatus. The vibration element 10 is any one of the vibration elements 11 to 16 described above. The light source device 981 including the three primary colors of RGB emits light whose intensity is modulated in accordance with a signal output from the control circuit 980 based on the image data. The light is two-dimensionally scanned by the vibration element 10 and the vertical scanning device 982 and projected onto the screen 983 as an image. The scanning speed of the vertical scanning device 982 is slower than that of the vibration element 10. For the vertical scanning device 982, for example, a galvanometer mirror that can perform positioning with high accuracy by non-resonant driving is used. Based on the control signal output from the control circuit 980, the drive circuit 801 included in the drive circuit 880 controls the scanning angle of the vibration element 10. Similarly, the scanning angle of the vertical scanning device 982 is controlled based on the output from the control circuit 980. Further, the drive circuit 802 of the drive circuit 880 outputs a mirror curvature control signal (drive signal), whereby the beam spot diameter on the screen 983 is maintained at a substantially constant size. Further, when the trapezoidal correction of the image is set through the input unit 984, the control circuit 980 changes the mirror curvature control signal in accordance with the change in the drive signal of the vertical scanning device 982. As a result, even when oblique projection is performed as shown in FIG. 14B, the focal length is increased in the scanning of the upper part of the screen, and the focal distance is shortened in the lower part, so that the beam spot diameter on the screen is set to a substantially constant size. Can be maintained.

  As described above, the image projection apparatus 8 using any of the vibration elements 11 to 16 can perform stable optical scanning and mirror curvature control without causing disconnection or abnormal vibration. For this reason, it is possible to exhibit the effects of constant speed and stabilization of the beam spot diameter by optimizing the maximum scanning angle and optimizing the mirror curvature control signal. As a result, highly accurate and reliable image projection is possible. Further, in the image projection device 8, the beam spot diameter can be made substantially constant on the screen even by oblique projection by adjusting the mirror curvature control signal. Thereby, the high-definition image projector 8 that can be used in a limited space can be realized.

[Optical pattern reader]
FIG. 15 shows an optical pattern reading device 9 which is an embodiment of the optical scanning device. The vibration element 10 is any one of the vibration elements 11 to 16. The light emitted from the light source 991 is reflected by the mirror member 301 of the vibration element 10 through the emission optical system 992, and scans the optical pattern. The reflected light whose intensity changes in accordance with the optical pattern is reflected again by the vibration element 10, collected by the detection optical system 994, and detected by the optical sensor 995. The decoder 996 binarizes the detection signal output from the optical sensor 995. Thereby, the information of the optical pattern is read. The drive circuit 890 outputs a drive signal for rotational vibration of the vibration element 10 and a mirror curvature control signal based on the signal from the control circuit 990. Thereby, the beam spot diameter is maintained at a substantially constant size on the projection surface having the optical pattern.

  The optical pattern reading device 9 using any of the vibration elements 11 to 16 can perform stable optical scanning and mirror curvature control without causing disconnection or abnormal vibration. For this reason, it is possible to exhibit the effects of constant speed and stabilization of the beam spot diameter by optimizing the maximum scanning angle and optimizing the mirror curvature control signal. As a result, highly accurate and reliable reading is possible.

[Summary]
According to the present embodiment, the piezoelectric material 401 has a first surface on which the first electrode 501 is formed and a second surface on which the second electrode 502 is formed. The first conductive member 201 is coupled to the first electrode 501, and the conductive first twisted beam 101 is coupled to the first conductive member 201 (203). The second conductive member 202 (204) is coupled to the second electrode 502, and the conductive second torsion beam 102 is coupled to the second conductive member 202. The mirror member 301 is fixed to the piezoelectric material 401 so as to sandwich the first conductive member 201 together with the piezoelectric material 401, and the curvature changes as the piezoelectric material 401 is deformed. Thus, in addition to the first conductive member 201 and the second conductive member 202, the first torsion beam 101 and the second conductive member 202 are made of a conductive material, so that no wiring is used. However, electric power can be supplied to the piezoelectric material 401. Therefore, defects such as disconnection are less likely to occur, and stable rotational vibration (swing) can be realized. Since the scanning mirror and the variable focus mirror are integrated, the optical scanning device can be expected to be downsized.

  By arranging the first torsion beam 101 and the second torsion beam 102 in parallel, the bending rigidity of the torsion beam increases. As a result, the scanning line is less likely to fluctuate in the sub-scanning direction (z direction), abnormal vibration can be reduced, and stable vibration can be realized. Note that the piezoelectric material 401 and the mirror member 301 may be cantilevered. A space may exist between the first torsion beam 101 and the second torsion beam 102. These configurations are difficult to change even when an impact is applied from the outside, and an effect of attenuating the change in a short time can be obtained.

  As shown in FIGS. 1A, 1B, 3, and 5 to 7, the first torsion beam 101 and the second torsion beam 102 exist on different sides of the piezoelectric material 401 and the mirror member 301, respectively. Thus, both the piezoelectric material 401 and the mirror member 301 may be supported. For example, the first torsion beam 101 supports the vibration unit 21 from the first direction, and the second torsion beam 102 supports the vibration unit 21 from the second direction (for example, a direction different from the first direction by 180 degrees). Also good. Such a double-sided support structure is larger in overall size than the cantilevered support structure, but has a higher flexural rigidity and makes it easier to suppress variations in the scanning line in the sub-scanning direction. On the other hand, the cantilever support structure is advantageous in terms of downsizing.

  As shown in FIG. 1B, the first torsion beam 101 is bent in the vicinity of the joint portion with the first conductive member 201, and the first torsion beam 101 in the longitudinal direction of the first torsion beam 101 is bent. The center line and the rotation axis of the vibration element 11 may substantially coincide with each other. Similarly, the second torsion beam 102 is bent in the vicinity of the joint with the second conductive member 202, and the center line in the longitudinal direction of the twelfth torsion beam and the rotation axis of the vibration element 11. And may substantially match.

  As described with reference to FIGS. 5 to 7, the first torsion beam 101 is coupled to the first conductive member 201 via the conductive first holding member that holds the first conductive member 201. You may do it. Thereby, the curvature change of the mirror member 301 etc. becomes difficult to reach to a torsion beam, and generation | occurrence | production of abnormal vibration can be reduced. Further, the first holding member may hold the first conductive member 201 at two locations that are symmetrical with respect to the rotation axis of the vibration element 11. This will further increase the effect of suppressing abnormal vibration.

  The second torsion beam 102 may be coupled to the second conductive member 202 via a conductive second holding member that holds the second conductive member 202. In addition, the second holding member may hold the second conductive member 202 at two locations that are symmetrical with respect to the rotation axis of the vibration element 11. As described above, a holding portion that suppresses abnormal vibration may also be employed for the second conductive member 202.

  As described with reference to FIGS. 6 and 7, the first conductive member 201 may be stored in a groove formed in the mirror member 301. This makes it possible to reduce the weight of the vibration unit 21. Similarly, the second conductive member 202 may be housed in a groove formed in the mirror member 301.

  As described with reference to FIGS. 6 and 7, the first torsion beam 101 is coupled to the first conductive member 201 via the conductive first holding member that holds the first conductive member 201. The second torsion beam 102 is coupled to the second conductive member 202 via the conductive second holding member that holds the second conductive member 202, and the first holding member And the second holding member may sandwich the magnet. A heavy object such as a magnet can be disposed at the center of the rotation shaft, and the vibration unit 21 can be more stably rocked.

  The first conductive member 201 may be a flat plate having a constant thickness. Similarly, the second conductive member 202 may be a flat plate having a constant thickness. Note that the shape of the first conductive member 201 and the shape of the second conductive member 202 may match, but the shapes of the two may be different as long as no abnormal vibration occurs.

  As described with reference to FIGS. 6 and 7, the first conductive member 201 may have a plurality of frames. Similarly, the second conductive member 202 may have a plurality of frames. Compared with the flat plate structure, the frame structure is advantageous in terms of weight reduction.

  As described with reference to FIG. 7, a plurality of frames may be crossed. Thereby, the difference between the curvature distribution in the scanning direction and the curvature distribution in the sub-scanning direction can be reduced. This will result in stable vibration.

  Note that drive circuits 801 and 802 that supply drive signals to the piezoelectric material 401 via any one of the vibration elements 11 to 16, the first torsion beam 101 and the second torsion beam 102 of the vibration element 11, and the vibration element 11 There may be further provided an optical scanning device that includes a magnetic field generation unit 700 that generates a magnetic field that oscillates the mirror unit, and that scans the light from the light source by the mirror member 301. By employing the vibrating elements 11 to 16, stable light scanning can be realized.

  The drive circuit may generate a drive signal by superimposing a signal having a frequency f2 that is twice the rotational vibration frequency f1 of the mirror member 301 and a signal having a frequency f4 that is four times. Thereby, a substantially constant beam spot diameter can be obtained regardless of the position.

  The rotation angle of the mirror member 301 may be ± 20 degrees or more. This is effective in reducing power consumption while widening the scanning angle of the mirror section.

  As described with reference to FIG. 13, an image forming apparatus 7 includes an optical scanning device and an image carrier, and forms an image on the image carrier with light scanned by the optical scanning device. May be provided. The image forming apparatus 7 using the vibration elements 11 to 16 is less likely to cause disconnection or abnormal vibration, and can perform stable optical scanning and mirror curvature control. For this reason, the effects of constant speed and stabilization of the beam spot diameter are exhibited by optimizing the maximum scanning angle and optimizing the mirror curvature control signal. That is, highly accurate and reliable image formation is possible. Further, in the image forming apparatus 7 using the vibration elements 11 to 16, the lens optical system for correcting the variation in the scanning speed can be simplified. In addition, it is not necessary to correct the image data or the intensity modulation signal of the laser beam in order to cope with fluctuations in the scanning speed. Thereby, a small and inexpensive image forming apparatus can be realized.

  As described with reference to FIG. 14, an image projection device 8 may be provided that projects an image on a screen by light scanned by the optical scanning device. The image projection apparatus 8 using any of the vibration elements 11 to 16 can perform stable optical scanning and mirror curvature control without causing disconnection or abnormal vibration. For this reason, it is possible to exhibit the effects of constant speed and stabilization of the beam spot diameter by optimizing the maximum scanning angle and optimizing the mirror curvature control signal. As a result, highly accurate and reliable image projection is possible. Further, in the image projection device 8, the beam spot diameter can be made substantially constant on the screen even by oblique projection by adjusting the mirror curvature control signal. Thereby, the high-definition image projector 8 that can be used in a limited space can be realized.

  As described with reference to FIG. 15, an optical pattern reading device 9 including an optical scanning device may be provided. The optical pattern reading device 9 using any of the vibration elements 11 to 16 can perform stable optical scanning and mirror curvature control without causing disconnection or abnormal vibration. For this reason, it is possible to exhibit the effects of constant speed and stabilization of the beam spot diameter by optimizing the maximum scanning angle and optimizing the mirror curvature control signal. As a result, highly accurate and reliable reading is possible.

Claims (25)

A piezoelectric material having a first surface on which a first electrode is formed and a second surface on which a second electrode is formed;
A first conductive member coupled to the first electrode;
A conductive first torsion beam coupled to the first conductive member;
A second conductive member coupled to the second electrode;
A conductive second torsion beam coupled to the second conductive member;
A vibration element comprising: a mirror member fixed to the piezoelectric material so as to sandwich the first conductive member together with the piezoelectric material, the curvature of which changes with deformation of the piezoelectric material.   2. The vibration element according to claim 1, wherein the first torsion beam and the second torsion beam are arranged in parallel to support the piezoelectric material and the mirror member in a cantilever manner.   The resonator element according to claim 2, wherein a space exists between the first torsion beam and the second torsion beam.   The first torsion beam and the second torsion beam are present on different sides of the piezoelectric material and the mirror member, respectively, so that both the piezoelectric material and the mirror member are supported. The vibrating element according to claim 1.   The first torsion beam is bent in the vicinity of the coupling portion with the first conductive member, and a longitudinal center line of the first torsion beam and a rotation axis of the vibration element are provided. Are substantially matched, and the second twisted beam is bent in the vicinity of the joint portion with the second conductive member, and the longitudinal center line of the second twisted beam and the second twisted beam The vibration element according to claim 4, wherein the rotation axis of the vibration element substantially coincides.   6. The first torsion beam is coupled to the first conductive member through a conductive first holding portion that holds the first conductive member. The vibration element according to any one of the above.   The vibrating element according to claim 6, wherein the first holding unit holds the first conductive member at two locations that are symmetrical with respect to a rotation axis of the vibrating element.   8. The second torsion beam is coupled to the second conductive member through a conductive second holding portion that holds the second conductive member. The vibration element according to any one of the above.   The vibration element according to claim 8, wherein the second holding portion holds the second conductive member at two positions that are symmetrical with respect to a rotation axis of the vibration element.   The vibration element according to claim 1, wherein the first conductive member is housed in a groove formed in the mirror member.   11. The vibration element according to claim 1, wherein the second conductive member is housed in a groove formed in the mirror member. The first torsion beam is coupled to the first conductive member via a conductive first holding portion that holds the first conductive member;
The second torsion beam is coupled to the second conductive member via a conductive second holding portion that holds the second conductive member;
The vibration element according to claim 1, wherein a magnet is sandwiched between the first holding part and the second holding part.   The vibrating element according to claim 1, wherein the first conductive member is a flat plate having a constant thickness.   14. The vibration element according to claim 1, wherein the second conductive member is a flat plate having a constant thickness.   The vibrating element according to claim 1, wherein the first conductive member has a plurality of frames.   16. The vibration element according to claim 1, wherein the second conductive member has a plurality of frames.   The vibrating element according to claim 15, wherein the plurality of frames intersect. A piezoelectric body having a piezoelectric layer interposed between a pair of electrodes;
A mirror member provided on at least one electrode side of the piezoelectric body and having a curvature that changes due to the deformation of the piezoelectric body;
A vibrating element comprising: a pair of conductive beam portions that support the mirror member and are electrically connected corresponding to each of the pair of electrodes.   The vibration element according to claim 18, wherein the mirror member has a curvature of a mirror surface that changes with the deformation of the piezoelectric body. The vibration element according to any one of claims 1 to 19,
A drive circuit for supplying a drive signal to the piezoelectric material via the first torsion beam and the second torsion beam of the vibration element;
And a magnetic field generation unit that generates a magnetic field for oscillating the mirror unit of the vibration element, and scans light from a light source with the mirror unit.   21. The optical scanning according to claim 20, wherein the driving circuit generates the driving signal by superimposing a signal having a frequency twice as high as a rotational vibration frequency of the mirror unit and a signal having a frequency four times as high as that of the mirror unit. apparatus.   The optical scanning device according to claim 20 or 21, wherein a rotation angle of the mirror portion is ± 20 degrees or more.   An image projection apparatus comprising the optical scanning device according to any one of claims 19 to 22, wherein an image is projected onto a screen by light scanned by the optical scanning device.   An image forming apparatus comprising: the optical scanning device according to any one of claims 19 to 22; and an image carrier, wherein the image is formed on the image carrier by the light scanned by the optical scanning device. apparatus.   An optical pattern reading device comprising the optical scanning device according to any one of claims 19 to 22.

Images